Sea Level Rise in Long Island Sound Over the Last Millennium
Abstract
Salt marshes along the north coast of Long Island Sound carry a detailed paleoenvironmental record, with information on relative sea level rise, climate and anthropogenic impacts (e.g., metal pollution). We studied fourteen salt marsh cores along the Sound, and here present data on cores from marsh islands in the mouth of the Connecticut River (Great Island) and the Housatonic River (Knells Island). Both are largely high-marsh environments, with a tidal range of 1.7 m at Great Island, 2 m at Knells Island. Cores are sliced in 2 cm intervals, dated with 210Pb, 137Cs and 14C, and benthic foraminifera are used as paleo sea level indicators. The records go back 600 years (Great Island) and 1500 years (Knells Island). Both locations show evidence for enhanced fresh water discharge around 1900 and 1950 AD, well-documented wet periods in the climate history of Connecticut. The relative sea level rise (RSLR) curve from Knells Island shows little change between 500 and 1000 AD, then the rate of RSLR accelerates until ~1600 AD to about 2.5 mm/year. From 1600 to 1700 AD, the curve is flat, then rises to about 1.7 mm/year, with an acceleration to 3 mm/year in the last 100 years. The Great Island RSLR curve shows a rate of 1.7 mm/year from 1400 AD on, with a short slow-down at ~1700 AD, and a slightly faster rate of 2.3 mm/year in the last 300 years. These data are similar to those in our other RSLR curves from the Long Island Sound marshes: RSLR rates are variable over the last 1000 years (~1 mm/year on average), and accelerate in the last 200-300 years to about 2.5-3 mm/year. The exact date of the beginning of the recent acceleration remains to be determined because it falls in the dating gap between viable 210Pb and 14C ages. Many curves show a slight decrease in rate of relative sea level rise around 1500-1600 AD, which we correlate with the coldest stretch of the Little Ice Age. The Knells Island core appears to show an acceleration around 1000 AD, which may correlate with the onset of the Medieval Warm period, but this signal is hard to discern in many other cores. A pronounced, short slow-down in the rate of relative sea level rise occurred around 600 AD in several cores. We tentatively correlate this episode with a coeval cold snap recorded in the GISP2 ice core record. The data thus suggest a direct link (no significant lag time) between climate change and rates of RSLR on the northeastern US seaboard.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMOS71D0323T
- Keywords:
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- 3020 Littoral processes;
- 3030 Micropaleontology;
- 4235 Estuarine processes;
- 4556 Sea level variations;
- 6334 Regional planning